This invention relates to a coupling for connecting metal tubes end-to-end to form tubular piles for use in pilings, in particular marine pilings for offshore platforms.
The invention is also concerned with a coupling of the type which comprises a male half-coupling and a female half-coupling attached to the ends of respective metal tubes and made fast with each other through clamping means.
In the implacement of marine pilings, with tubular metal piles of large diameters, comprising a plurality of metal tubes connected together end-to-end fashion, it is of special import that couplings be provided at the ends of said tubes which can be tightened and if need be loosened in a particularly quick and effective manner.
The coupling fast tightening feature is made necessary by the high hourly cost of the equipment involved in implacing the piling, whilst the need for effective tightening, and specifically the possibility of developing an axial preload between the male and female half-couplings, is imposed by the tubular piling implacement technology.
One example of couplings useful in the implacement of tubular piling is disclosed in U.S. Pat. No. 4,094,539 of June 13, 1978.
That coupling comprises male and female half-couplings: the female half is provided with a plurality of latches which are movable radially independently of one another to and from the male half. That end of each of the latches which is laid facing the male half-coupling is cut to profile with one or more teeth adapted to engage with one or more annular grooves formed on the male half. The contact surfaces of the latch teeth and corresponding annular grooves are tapering surfaces, thereby an advantageous axial preload action is developed in fitting the coupling halves together.
In view of the large diameter of a pile intended for driving into the sea bottom, a tight coupling of the tubes comprising it dictates the availability of a large number of latches for independent operation of one another.
As a consequence, the coupling closing and/or opening operation is time-consuming, while the axial preload aimed at between the coupling halves is inaccurate and unevenly applied, especially because the radial tightening stresses at each latch are adjusted independently of one another.